Security container

ABSTRACT

A portable security container adapted to contain valuable articles and comprising a lock which when opened permits access to the interior of the container, a security circuit comprising a plurality of gating circuits, means adapted to apply a voltage from a voltage source within the container to each gating circuit to render it conductive, a further circuit which can take more than one state and which is arranged to change state if the voltage is not applied to the gating circuits in a predetermined sequence, and if the lock is opened before a predetermined number of gating circuits have been rendered conductive, means adapted to destroy or characteristically mark the contents of the container upon said change of state of the further circuit, and voltage-sensing means to cause the further circuit to change state if the said voltage falls below a predetermined value.

United States Patent 1,606,516 11/1926 Daly Inventors Edward A. MuntonThorpe Bay. Essex; Alan Birt Acres, Leigh-on-sea Essex, England Appl.No. 841,878 Filed July 15, 1969 Patented Feb. 2, 1971 Assignee VigilSecurity Limited Sussex, England a British company Priority July 18,1968 Great Britain 34283/68 SECURITY CONTAINER 10 Claims, 7 DrawingFigs.

US. Cl 109/25, 109/42, 109/44; 317/134 Int. Cl E05g 3/00 Field of Search109/25, 29, 35, 42, 44; 70/278; 317/134, 135; 340/280 References CitedUNITED STATES PATENTS Primary Examiner-David .l Williamowsky AssistantExaminerPhilip Cl Kannan Atr0rney-Cushman, Darby & Cushman ABSTRACT: Aportable security container adapted to contain valuable articles andcomprising a lock which when opened permits access to the interior ofthe container, a security circuit comprising a plurality of gatingcircuits, means adapted to apply a voltage from a voltage source withinthe container to each gating circuit to render it conductive, a furthercircuit which can take more than one state and which is arranged tochange state if the voltage is not applied to the gating circuits in apredetermined sequence, and if the lock is opened before a predeterminednumber of gating circuits have been rendered conductive, means adaptedto destroy or characteristically mark the contents of the container uponsaid change of state of the further circuit, and voltage-sensing meansto cause the further circuit to change state if the said voltage fallsbelow a predetermined value.

PATENTEDFEB mm SHEET 1 [IF 5 SECURITY CONTAINER This invention relatesto a portable security container.

In one aspect, although not so restricted. the invention provides aportable security container adapted to contain valuable articles andcomprising a lock which when opened permits access to the interior ofthe container. a security circuit comprising a plurality of gatingcircuits. means adapted to apply a voltage from a voltage source withinthe container to each gating circuit to render it conductive, a furthercircuit which can take more than one state and which is arranged tochange state either if the voltage is not applied to the gating circuitsin a predetermined sequence. or if the lock is opened before apredetermined number of gating circuits have been rendered conductive.means adapted to destroy or characteristically mark the contents of thecontainer upon said change of state of the further circuit, andvoltage-sensing means to cause the further circuit to change state ifthe said voltage falls below a predetermined value.

There may be a selector device having a plurality of outputs. some ofwhich are selectable to apply respectively the said voltage torespective gating circuits, other outputs being connected to the furthercircuit whereby if a said output is selected and the said voltageapplied thereto. the further circuit changes state.

The gating circuits may be arranged in cascade. an input terminal ofeach gating circuit being respectively connected to one terminal of thevoltage source. the input terminals of the gating circuits, with theexception of the input terminal of that gating circuit forming the firstcascade stage. each also having a respective parallel connection to anoutput terminal of the gating circuit of the preceding cascade stage,the said predetermined sequence starting with the gating circuit formingthe last cascade stage and finishing with the gating circuit forming thefirst cascade stage.

The input terminal of each gating circuit may be an anode terminal, theoutput terminal being a cathode terminal, each gating circuit alsohaving a respective control terminal, the control terminal beingconnected to the respective cathode terminal via a bias resistor and,except in the gating circuit forming the last cascade stage, beingadapted to receive respectively the said voltage via a respectiveunilaterally conductive device arranged so that it only conducts if thepotential at the control terminal is less than the potential at theanode terminal, the said voltage, when the said device is nonconductivebeing fed to the said further circuit to change the state thereof.

The said further circuit may comprise at least one siliconcontrolledrectifier, the cathode terminal of the gating circuit forming the laststage of the cascade being connected to the other terminal of thevoltage source, the cathode of a siliconcontrolled rectifier of thefurther circuit also being connected to the said other terminal via azener diode.

The cathode of the said silicon-controlled rectifier of the furthercircuit may be connected to the said one terminal of the voltage sourcevia a further bias resistor, in parallel with its connection to the saidother terminal.

The further circuit may comprise a control terminal to which areconnected, in parallel, the said other outputs of the selector deviceand respective leads each adapted to receive the said voltage when thesaid respective unilaterally conductive device is nonconductive.

The voltage-sensing means may be adapted to compare a first voltagehaving a fixed relation to the voltage of the voltage source with asecond substantially constant voltage, a trigger means causing thefurther circuit to change state when the first voltage becomes less thanthe second voltage.

There may be a potential divider connected across the terminals of thevoltage source to derive the first voltage, the second voltage being theZener voltage of the said Zener diode.-

The further circuit may comprise an explosive fuse which is arranged toexplode when the further circuit changes state to release into theinterior of the container an indelible dye or a corrosive substance.

The security container may be provided with a guard circuit comprisingan electrically continuous elongated convoluted conductor. and at leastone open-circuitcd elongated convoluted or branched conductor closelyproximate the continuous conductor but insulated therefrom, the furthercircuit being adapted to change state in response to a change in theresistance of the continuous conductor. or to change state if continuityis established between an open-circuited conductor and the continuousconductor.

The conductors may be arranged in two layers, coextensive with eachother and with the wall. the continuous conductor and at least one saidopen-circuited conductor being provided in each layerv The invention isalso directed to any novel feature or combination of features hereindescribed and/or shown in the drawings.

The invention will be described. merely by way of example, withreference to the accompanying drawings, wherein:

FIG. I shows a security container according to the invention;

FIGS. 2a and 2b show a security circuit incorporated in the container ofFIG. 1, FIGS. 2a and 2b interconnecting at A, B, C;

FIG. 3 shows part of the structure of FIG. 1',

FIGS. 3a and 3b are scrap plan sections of parts of the containerincorporating the structure of FIG. 3. in two different embodiments; and

FIG. 4 shows a further circuit incorporated in the container of FIG. 1.FIGS. 2b and 4 interconnecting at D.

FIG. I shows a security container 10 comprising an outer casing 12 and aremovable inner tray 14, both of toughened glass fibre. The inner tray14 has a recess or compartment 16 for containing valuable articles,particularly cash or negotiable bonds. The tray 14 is a sliding fitwithin the outer casing 12. and has a flanged end face 18 which abutsthe end 20 of Y the outer casing 12 when the tray 14 is receivedtherein. The

tray 14 is locked inside the outer casing 12 by means of a suitablyhigh-quality (e.g. 10 lever) lock 22 in the end face 18 of the tray.Alternatively, the lock 22 may be a magnetic or electrostatic lock. Thecontainer 10 is provided with a handle 24 for transportation thereof.

The inner tray comprises in its recess 16 and attached to one of thebounding walls thereof an explosive black powder fuse 26 which isarranged to explode if an unauthorized entry to the container isattempted. Adjacent the fuse 26 is a dye container 28 containing aquantity of indelible dye. The container 28 and fuse 26 are separated byonly a thin membrane such that if the fuse is detonated, the explosionforcibly disperses the dye throughout the recess 16, drenching itscontents. The dye is of a characteristic color, rendering the contentsof the container 10 instantly recognizable and, if cash, worthless to athief. Alternatively a corrosive substance, e.g. acid may be substitutedif it is preferred to completely destroy the contents of the container10 rather than to allow an unauthorized person access to them in anyform. This is of use if the contents of the container are classifieddocuments.

FIGS. 2a and 21; show the security circuit incorporated in the container10 to react to attempted unauthorized access to the contents thereof.

The lock 22 comprises a normally open key-operated switch (30 FIG. 2a)which is closed when the key is inserted in the lock and turned. If thesecurity circuit of FIG. 3 has not previously been set in apredetermined condition, closing the switch 30 explodes the fuse 26.

The security circuit comprises a voltage source 32, e.g. a 12 v. drybattery housed in the recess 16 of the container. Across the battery 32are connected in cascade a plurality of gating circuits 34, 36, 38, 40.Each gating circuit comprises a siliconcontrolled rectifier 35, 37, 39,41, the input or anode terminals of which are respectively connected tothe positive terminal of the battery 32 via respective resistors 42, 44,46, 48. With the exception of the silicon-controlled rectifier 35 of thegating circuit 34 forming the first cascade stage, the anode of eachsilicon-controlled rectifier 37, 39, 41 of each cascade stage is alsoconnected to the output or cathode terminals of the siliconrcontrollcdrectifier of the preceding cascade stage. this connection being inparallel with the connection of the silicon-controlled rectifier to thepositive terminal of the battery via the appropriate resistor 44. 46.48.

The anode of silicon-controlled rectifier 35 of the first cascade stage34 is connected. in parallel with its connection to the positiveterminal of the battery. via the key-operated switch 30 to asilicon-controlled rectifier 50 forming part of a further circuitincorporating the fuse 26. The anode of the silicon-controlled rectifier50 is connected via the fuse 26 to the positive terminal of the battery32, The cathode of the rectifier 50 is connected via a Zener diode 52 tothe batterys negative terminal, and to its positive terminal via aresistor 54.

The control or gating terminals of the silicon-controlled rectifiers 35.37, 39, 41 are respectively biased from their respective cathodes viarespective gate resistors 60, 62. 64, 66 and are also respectivelyconnected to respective selectable outputs T,,, T T and T of alO-position rotary selector switch 70 provided on the end face 18 of theinner casing 14 (FIG. 1). I

The connections of the control terminals of the silicon-controlledrectifiers 35, 37, 39 to the outputs T T T are via respectiveunilaterally conductive diodes 74, 76, 78.

The remaining selectable outputs T T T T T T are connected via a commonline passing through a unilaterally conductive diode 72 to the controlterminal of the silicon-controlled rectifier 50.

The outputs T T T are also connected to the control terminal of thesilicon-controlled rectifier via respective leads from the anodes of thediodes 74, 76, 78 via further diodes 75, 77, 79.

The rotary switch 70 is connected via a push button switch 80 (FIG. 1)on the end face 18 of the inner tray 14 to the battery positiveterminal. Thus, by operating the rotary selector switch and brieflyclosing the switch 80, a voltage pulse can be emitted from a chosenselectable output T,,-T,,.

Assuming the container to be closed and locked, the security circuitpermits the container to be unlocked and opened only if the outputs T TT and T are selected in that order and the switch 80 briefly closedafter each selection.

The circuit operates as follows: when the selectable output T, isselected and the switch 80 briefly closed, a voltage pulse is applied tothe control tenninal of the silicon-controlled rectifier 41, renderingit conductive and reducing the voltage at the cathode of thesilicon-controlled rectifier 39. If the output T is then selected andthe switch 80 briefly closed a voltage pulse is applied to thesilicon-controlled rectifier 39, rendering it in turn conductive. 1f theoutputs T and T are selected in turn and a similar procedure adopted,then all four silicon-controlled rectifiers 35, 37, 39, 41 are renderedconductive. When the silicon-controlled rectifier 35 is conductive, thevoltage at its anode is reduced. The resistances 42, 44, 46, 48 arechosen such that this anode voltage is suffi' ciently reduced that ifthe key switch 30 were closed the voltage applied to the controlterminal of the silicon-controlled rectifier 50 would not be sufficientto make it conduct. Conversely, if the key switch 30 is closed beforethe silicon-controlled rectifier 35 is conducting, a much higher voltageis applied to the silicon-controlled rectifier 50, causing it to conductand exploding the fuse 26. Thus, if the key switch is operated before apredetermined number (i.e. four) of the gating circuits 34, 36, 38, 40have been rendered conductive the further circuit comprising thesilicon-controlled rectifier 50 and the fuse 26 changes state.

1f the outputs T,, T T T are not selected in the correct order, thenagain the fuse 26 is made to explode. For example, if a given gatingcircuit (e.g. 38) is not conducting, then the cathode of thesilicon-controlled rectifier (e.g. 37) of the preceding gating circuit36 is at the full positive voltage developed by the battery, since thegating circuit 38 represents an infinite impedance. Consequently, thecontrol terminal of the silicon-controlled rectifier 37 is also atsubstantially the full battery voltage, being connected from its cathodevia the gate resistor 64. Thus when a voltage pulse is wrongly appliedvia output T to the diode 76, there is no potential drop across thediode which therefore does not conduct. The pulse instead passes via thediode 77 to the siliconcontrolled rectifier 50. causing it to conductand explode the fuse 26.

Thus. if the voltage pulses are not applied to the gating circuits in apredetermined sequence starting with the gate 40 forming the last stageof the cascade and finishing with the gate 34 forming the first cascadestage, the further circuit 50, 26 changes state. l 3

The resistor 54 and the Zener diode 52 ensure that the maximum forwardvoltage drop of the silicon-controlled rectifiers 35, 37, 39, 41 inseries is not quite sufficient to cause the silicon-controlled rectifier50 to conduct.

if any of theremaining outputs T T T T T T, are selected then thevoltage pulse is applied directly to the control terminal of thesilicon-controlled rectifier 50, exploding the fuse 26.

In order to prevent a prospective thief gaining access to the interiorof the container by keeping it until the battery is ex hausted, thesecurity circuit embodies a voltage sensing circuit including a triggerto explode the fuse 26 if the battery voltage falls below apredetermined value.

A potential divider 84, 86 is disposed across the battery terminals, andbiases the emitter of a transistor 88 at a constant fraction of thebattery voltage. The base of the transistor 88 is connected to thejunction of the Zener diode 52 and the re-' sistor 54 and is initiallyat a lower potential than the'ernitter. The potential at the base isthus the Zener voltage and is substantially constant. 7

As the battery voltage falls with time, the emitter voltage oftransistor 88, initially greater than the base voltage, finally fallsbelow a substantially constant voltage which is the Zener voltage minusthe emitter-base bias voltage (characteristic of the transistor)necessary for the transistor 88 to conduct. The transistor 88 thenconducts, switching on a further transistor 90 and applying a voltage.via the emitter-collector circuit thereof to the control terminal of therectifier 50. The rectifier 50 conducts, exploding the fuse 26.

A large capacitor 92 is provided across the battery terminals to ensurethat sufficient energy is available, even when after a considerable lifethe impedance of the battery has increased, to explode the fuse 26 whenthe rectifier 50 conducts,

Disposed at the walls of the outer container 12 and the tray 14(including the end face 18 thereof) is a guard circuit such that anattempt to cut, burn or otherwise penetrate the walls of the containerwill result in the fuse 26 exploding. in this embodiment, the guardcircuit is embedded in the walls by being moulded therein.

The guard circuit (FIG. 3) comprises two parallel layers 94 of closelyspaced conductors (e.g. copper wires or strips), the layers beingcoextensive with each other and with the walls. One conductor 96 iselectrically continuous and is convoluted, e.g. foldedback upon itself.Each layer comprises two further open-circuited conductors 98, 100having a plurality of opencircuited branches. It will be appreciatedthat the open-circuited conductors 98,- 100 alternatively, or inaddition to being branched may be convoluted, provided they remain, as awhole, open-circuited. The conductors 96, 98, 100 are electricallyseparate from each other, being insulated by the glass fibre in whichthey are embedded.

The conductors 98, 100 are each connected at one end to a respectivecommon lead 102, 104. The other (branched) ends 106, 108 of thesesconductors are left electrically discontinuous, that is to sayunconnected or floating."

The conductors 96,98, 100 have spaced-apart parallel portions. Theparallel portions of the conductor 96 are interposed between similarlyspaced-apart neighboring parallel portions of the conductors 98, 100.Consequently, an attempt to cut or drill through the walls of thecontainer will result in the conductor 96 being severed, and/orcontinuity or a short circuit being established between adjacentportions of the conductors 96 and 98 or 100. exploding the fuse 26 asdescribed hereinafter. Such a short circuit can of coursc occur betweenthe conductors 96. 98, 100 of different layers. 7 Although theconductors are shown as laminarly arranged in FIG. 3, they can of coursebe wrinkled in the plane of the drawing, to combat attempts to grindaway the surface of the container wall until the guard circuit iscompletely exposed.

Referring to FIG. 3a, which shows a scrap section through a wall 93taken perpendicularly to the conductors in the layers 94, it will beseen that the layers 94 are disposed relative to each other in the wall93 so that the parallel portions of the conductors of one layer arealigned behind the parallel portions of the conductors of the otherlayer (i.e. directly one behind the other) when viewed normally of thelayers. This conductor-for-conductor alignment results in the conductorspresenting a confusing pattern if an attempt is made to X-ray thecontainer 10 to investigate its construction.

. FIG. 3b shows an alternative-arrangement of the parallel portions ofthe conductors. The parallel portions of the conductors of one layer 94are offsetrelative to the parallelportions of the conductors of theother layer, so as to be aligned I conductors are arranged as in FIG. 3aor 3b. The conductor 96 is continuous throughout the repetitions of thepattern. The

conductor 96 also extends. through the other layer 94, although ifdesired a separate conductor 960 could be used, and connected in serieswith the conductor 96 as described hereinafter, to form an electricallycontinuous conductor. The exact number of layers, and the number ofconductors in each layer is a matter of choice. Thus more than twoopen-circuited conductors could be provided.

The guard circuit may extend by means of for example a connector acrossat least'one of the interfaces between the outer casing 12 and the innertray 14, so that any significant relative movement of the tray 14 andcasing 12 (such as would occur if the tray was withdrawn from thecasing) whilst the guard circuit is active breaks the continuity of theconductor 96 and results in the fuse 26 exploding.

The electrically continuous conductor 96 is connected in series with andthus efiectively forms part of the potential divider 84, 86 of thetrigger circuit shown in FIG. 2. Any further sontinuous conductors 96amay also be similarly connected. If she continuity of the conductor 96is broken, or if its resistance issignificantly increased due to itbeing partially cut through, then the voltage at the emitter oftransistor 88 is decreased, as if the battery 32 were'exhausted, and thesiliconcontrolled rectifier 50 is caused to conduct, as describedhereinbefore, exploding the fuse 26.

The conductors 98, 100 are connected via their common leads 102, 104 tothe control terminal of the silicon-controlled rectifier 50 (FIG. 2b).Normally there is no electrical continuity between the conductor 96 andthe conductors 98, 100 and there is a very high resistance therebetween.If continuity is established however, e.g. by a would-be thief trying todrill through the container 10 by means of a metal drill, or byattempting to bypass the continuous conductor 96 by injecting into thewall of the container 10 a conductive fluid, the positive batteryvoltage is applied via the conductors 98, 100 to the silicon-controlledrectifier 50, exploding the fuse 26.

A pair of thermostats 108, 110 are provided on an inside wall of theinner tray 14. Each comprises a respective pair of normally opencontacts, one pair becoming closed if the tem' perature of the container10 exceeds a predetermined value, the other pair becoming closed if thetemperature of the container 10 falls below a second lower predeterminedvalue (e.g.

if an attempt is made to freeze the dye in the dye container 28). Thepairs of contacts are connected in parallel between the battery positiveterminal and the control terminal of the rectifier 50. Thus if eitherpair of contacts close. the fuse 26 explodes.

The container 10 is also provided with a priming circuit which allowsthe container to be handled when opened by authorized persons. Thepriming circuit comprises a normally open push button switch 112 (FIGS.1 and 2h) connected in the main lead from the positive terminal of thebattery. When the switch 112 is open. the security circuit of FIGS. 20and 2h isolated from the battery and from the capacitor 92. A relay 113which is energized when the switch 112 is closed, is provided with apair of hold-on contacts in parallel with the switch 112. Thus, once theswitch 112 has been briefly closed. the security circuit remainsconnected to the battery and the capacitor 92. A capacitor 114 isprovided across the control and cathode terminals of the rectifier 50 toprevent any stray voltage surge that may occur when the switch 112 isclosed, from causing the rectifier to conduct and exploding the fuse 26.4

The lock 22 comprises a second key-operated switch 116 (FIG. 2b) havingnormally closed contacts. The lock is such that when the key is turnedtherein, the key operated switch 30 closes before switch 116 opens.

The switch 116 is in series with the contacts 118, and when open thusdeenergizes the relay 113. allowing the inner tray 14 to be withdrawnwithout the fuse 26 being exploded when the continuity of the conductor96 is interrupted.

A modification of the security circuit is shown in FIG. 4. Thismodification makes the further circuit 50. 26 also change state inresponse to a significant change in another electrical property of theguard circuit, its capacitance.

In order to detect capacitance change, an alternating voltage isprovided by an oscillator 120. The alternating voltage is typicallysinusoidal at a frequency of 1,000 Hz. The oscillator 120 comprises apair of transistors 122, 124, the bases of which are connected via acenter tapped secondary winding 128 of a three-winding transformer 126and a resistor 130 to the positive terminal of the battery 32. Thecollectors of the transistors 122, 124 are similarly connected via acentertapped primary winding 132 of the transformed and a choke 136. Thechoke 136 is a constant current device, enabling the oscillator toproduce a sinusoidal output. An approximately square wave output wouldbe obtained if the choke were omitted.

The output of the oscillator 120 is applied via a DC blocking capacitor137 across a balanced capacitance bridge 138 (e.g. a Wien bridge). Athird winding 139 of the transformer 126 is also connected across thebridge 138 as shown in FIG. 4.

The bridge 138 has one of its arms" the self capacitance of the guardcircuit as measured for example between the conductor 96 and theconductors 98 and/or 100. The remaining capacitances of the bridge arechosen so that the bridge is balanced and produces no output in itsdifference circuit. However, if the container 10 is tampered with andthe capacitance between the conductor 96 and the conductors 98, 100changes significantly (e.g. due to a wall of the container beingdeformed, or by the glass fibre insulation being partially cut away)then the bridge 138 becomes unbalanced, and produces an output. Thisoutput is amplified in an AC amplifier 140 rectified in a diode 142 andfed to a Schmitt trigger 144.

The Schmitt trigger 144 comprises a pair of transistors 146, 148, theemitters .of which are biased from the negative terminal of the battery32 via a bias resistor 15. The collector of the transistor 146 isconnected to the base of the transistor 148 via a potential dividercomprising resistors 152, 154. A capacitor 156 bridges the resistor 154.

The amplified rectified output of the bridge 138 is applied to the baseofthe transistor 146, and if it is above a predetermined threshold levelchosen by suitably selecting the values of the components of the Schmitttrigger 144, the transistors 146 and 148 conduct, and apply a signal tothe control terminal of the silicon-controlled rectifier 50. thusdetonating the fuse 26.

The capacitor 156 is provided to compensate for any stray capacitancebetween the base of the transistor 148 and earth (the negative terminalof the battery 32). Such a stray capacitance would reduce the steepnessof the wave front of the pulse emitted by the transistor 146 when itstarts to conduct with the result that the Schmitt trigger 144 may failto trigger if a short pulse. c.g. of order milliseconds were applied tothe base of the transistor 146.

An integrating capacitor 158 ensures that spurious transient signals(e.g. of order microseconds) that may be above the threshold level donot trigger the Schmitt trigger 144 and detonate the fuse 26. I

The security container 10 specifically described herein by way ofexample only may have the advantage that once closed and locked by meansof the lock 22, a messenger carrying the container is not required toresist an attempt to steal the container, since the thief could not gainentry to the container. Consequently, the messenger need not have thecontainer 10 chained to his wrist, as is often the practice with knowncontainers. Furthermore, the messenger need. not take any action toprotect the box, or to set off any alarm. The messenger is thus lessexposed to physical danger.

It will be appreciated that the invention is applicable to other thanportable containers. For example, it may be applied to a safe, eitherfreestanding or incorporated into a building, e.g. as a vault. it mayalso be applied to a vehicle such as a van used for transporting largeamounts of cash.

We claim:

l. A portable security container adapted to contain valuable articlesand comprising a lock which when opened permits access to the interiorof the container, a security circuit compris-' ing a plurality of gatingcircuits, a voltage source within the container, means to apply avoltage from said source to each gating circuit to render it conductive,a further circuit which can take more than one state and which isadapted to change state if the voltage is not applied to the gatingcircuits in a predetermined sequence, and if the lock is opened before.a predetermined number of gating circuits have been renderedconductive, means controlled by the further circuit and adapted todestroy or characteristically mark the contents of the container uponsaid change of state of further circuit, and voltage-sensing means tosense said voltage and adapted to cause the further circuit to changestate if the said voltage falls below a predetermined value.

2. A portable security container as claimed in claim 1 and comprising aselector device having a plurality of outputs, some of which areselectable to apply respectively the said voltage to respective saidgating circuits, other outputs being connected to the further circuitwhereby if a said other output is selected and the said voltage appliedthereto, the further circuit changes state.

3. A portable security container as claimed in claim 1 wherein thegating circuits are arranged in cascade, an input terminal of eachgating circuit being respectively connected to one terminal of thevoltage source, the input terminals of the gating circuits, with theexception of the input terminal of that gating circuit forming the firstcascade stage. each also having a respective parallel connection to anoutput terminal of the gating circuit of the preceding cascade stage,the said predetermined sequence starting with the gating circuit formingthe last cascade stage and finishing with the gating circuit forming thefirst cascade stage.

4. A portable security container as claimed in claim 3 wherein the inputterminal of each gating circuit is an anode terminal, the outputterminal being a cathode terminal, each gating circuit also having arespective control terminal. the control terminal being connected to therespective cathode terminal via a bias resistor and, except in thegating circuit forming the last cascade stage, being adapted to receiverespectively the said voltage via a respective unilaterally conductivedevice adapted to conduct only if the potential at the control terminalis less than the potential at the anode terminal, and means to feed thesaid voltage, when the said device is nonconductive. to the said furthercircuit to change the state thereof.

5. A portable security container as claimed in claim 4 wherein the saidfurther circuit comprises at least one silicon controlled rectifier, thecathode terminal of the gating circuit forming the last stage of thecascade being connected to the other terminal of the voltage source, thefurther circuit comprising a silicon-controlled rectifier, the cathodeof which is also connected to the said other terminal via a Zener diode.

6. A portable security container as claimed in claim 5 wherein thecathode of the said silicon-controlled rectifier of the further circuitis connected to the said one terminal of the voltage source via afurther bias resistor, in parallel with its connection to the said otherterminal.

7. A portable security container as claimed in claim 4, comprising aselector device having a plurality of outputs, some of which areselectable to apply respectively the said voltage to respective gatingcircuits, other said outputs being connected to a control terminal ofthe further circuit, there also being connected to said terminalrespective leads each adapted to receive the said voltage when the saidrespective unilaterally conductive device is nonconductive.

8. A portable security container as claimed in claim 1 comprising meansto provide a first voltage having a fixed relation to the voltage of thevoltage source and means to provide a second substantially constantvoltage, the sensing means being adapted to compare said first andsecond voltages, the sensing means comprising trigger means adapted tocause the further circuit to change state when the first voltage becomesless than the second voltage.

9. A portable security container as claimed in claim 8 comprising apotential divider connected across the terminals of the voltage sourceto derive the first voltage, and a Zener diode, the second voltage beingthe Zener voltage of the said Zener diode.

10. A portable security container as claimed in claim 1 wherein thefurther circuit comprises an explosive fuse, means to explode said fusewhen the further circuit changes state to release into the interior ofthe container an indelible dye or a corrosive substance.

1. A portable security container adapted to contain valuable articlesand comprising a lock which when opened permits access to the interiorof the container, a security circuit comprising a plurality of gatingcircuits, a voltage source within the container, means to apply avoltage from said source to each gating circuit to render it conductive,a further circuit which can take more than one state and which isadapted to change state if the voltage is not applied to the gatingcircuits in a predetermined sequence, and if the lock is opened before apredetermined number of gating circuits have been rendered conductive,means controlled by the further circuit and adapted to destroy orcharacteristically mark the contents of the container upon said changeof state of further circuit, and voltage-sensing means to sense saidvoltage and adapted to cause the further circuit to change state if thesaid voltage falls below a predetermined value.
 2. A portable securitycontainer as claimed in claim 1 and comprising a selector device havinga plurality of outputs, some of which are selectable to applyrespectively the said voltage to respective said gating circuits, otheroutputs being connected to the further circuit whereby if a said otheroutput is selected and the said voltage applied thereto, the furthercircuit changes state.
 3. A portable security container as claimed inclaim 1 wherein the gating circuits are arranged in cascade, an inputterminal of each gating circuit being respectively connected to oneterminal of the voltage source, the input terminals of the gatingcircuits, with the exception of the input terminal of that gatingcircuit forming the first cascade stage, each also having a respectiveparallel connection to an output terminal of the gating circuit of thepreceding cascade stage, the said predetermined sequence starting withthe gating circuit forming the last cascade stage and finishing with thegating circuit forming the first cascade stage.
 4. A portable securitycontainer as claimed in claim 3 wherein the input terminal of eachgating circuit is an anode terminal, the output terminal being a cathodeterminal, each gating circuit also having a respective control terminal,the control terminal being connected to the respective cathode terminalvia a bias resistor and, except in the gating circuit forming the lastcascade stage, being adapted to receive respectively the said voltagevia a respective unilaterally conductive device adapted to conduct onlyif the potential at the control terminal is less than the potential atthe anode terminal, and means to feed the said voltage, when the saiddevice is nonconductive, to the said further circuit to change the statethereof.
 5. A portable security container as claimed in claim 4 whereinthe said further circuit comprises at least one silicon-controlledrectifier, the cathode terminal of the gating circuit forming the laststage of the cascade being connected to the other terminal of thevoltage source, the further circuit comprising a silicon-controlledRectifier, the cathode of which is also connected to the said otherterminal via a Zener diode.
 6. A portable security container as claimedin claim 5 wherein the cathode of the said silicon-controlled rectifierof the further circuit is connected to the said one terminal of thevoltage source via a further bias resistor, in parallel with itsconnection to the said other terminal.
 7. A portable security containeras claimed in claim 4, comprising a selector device having a pluralityof outputs, some of which are selectable to apply respectively the saidvoltage to respective gating circuits, other said outputs beingconnected to a control terminal of the further circuit, there also beingconnected to said terminal respective leads each adapted to receive thesaid voltage when the said respective unilaterally conductive device isnonconductive.
 8. A portable security container as claimed in claim 1comprising means to provide a first voltage having a fixed relation tothe voltage of the voltage source and means to provide a secondsubstantially constant voltage, the sensing means being adapted tocompare said first and second voltages, the sensing means comprisingtrigger means adapted to cause the further circuit to change state whenthe first voltage becomes less than the second voltage.
 9. A portablesecurity container as claimed in claim 8 comprising a potential dividerconnected across the terminals of the voltage source to derive the firstvoltage, and a Zener diode, the second voltage being the Zener voltageof the said Zener diode.
 10. A portable security container as claimed inclaim 1 wherein the further circuit comprises an explosive fuse, meansto explode said fuse when the further circuit changes state to releaseinto the interior of the container an indelible dye or a corrosivesubstance.